1. Field of the Invention
This invention relates to a method and apparatus for adhering a tape or sheet to a semiconductor wafer.
2. Description of the Related Art
In the production of semiconductor devices, such as integrated circuits (IC), large scale integrated circuits (LSI), and very large scale integrated circuits (VLSI), a disk-like semiconductor wafer is formed with a number of electrical patterns on the surface thereof and then cut into a predetermined number of squares to obtain semiconductor chips for individual devices. The cutting is usually effected by a diamond cutter in a so-called dicing process. However, before the cutting, an adhesive-backed tape or sheet is conventionally adhered to the back surface of the wafer to prevent cut chips from scattering into individual pieces.
When adhering the tape or sheet to the back surface of the wafer, if an excessive pressure is used to press the tape against the wafer, the wafer surface will be damaged, or it will become difficult to obtain uniform adhesion between the tape and wafer. Therefore, an improved technique for uniformly adhering a tape or sheet to a semiconductor wafer has long been desired.
A method for adhering a tape to a wafer is known in the prior art, in which method a patterned semiconductor wafer is placed on a wafer supporting table and an adhesive-backed tape, made of, for example, vinyl chloride, is then brought into contact with the wafer surface. Then, the entire surface of the adhesive-backed tape is rolled or brushed with a rubber roller or brush. However, in this method, there is a disadvantage in that the patterned surface of the wafer which is in contact with the supporting table could be damaged by a physical pressure applied to the back surface of the wafer by this rolling or brushing. In addition, air bubbles might form between the tape and wafer, thus preventing a uniform adhesion of the tape to the wafer.
In another known method, a patterned semiconductor wafer is placed on a wafer supporting table in a vacuum chamber. In the vacuum chamber, an adhesive-backed tape is brought into contact with the wafer by a pressure difference created on the respective sides of the tape. According to this method, air bubbles are prevented from forming between the tape and wafer. However, this method has a disadvantage in that the patterned surface of the wafer which is contact with the supporting table could be damaged when the tape is pressed against the wafer by the pressure difference applied to the tape.